This invention relates to a radio frequency tuner and more particularly but not by way of limitation to an electrically controlled radio frequency tuner using a signal waveguide housing having a ferromagnetic fluid therein which is controlled by a plurality of magnets attached to the exterior of the waveguide housing.
Heretofore, there have been various types of devices used for magnetically controlling ferromagnetic fluids in waveguide sections. These devices are described in the following U.S. patents. U.S. Pat. No. 3,956,938 to Carrico, U.S. Pat. No. 3,001,154 to Reggia, U.S. Pat. No. 2,532,157 to Evans, U.S. Pat. No. 2,798,207 to Reggia, U.S. Pat. No. 4,188,594 to Bongianni and a 1949 Article to Miller. None of these prior art devices specifically use controlled electromagnets for partially blocking or blocking the cavity of the waveguide housing.
Heretofore, reflections and circulator feedthrough in a radio frequency system using a common antenna for both the transmitter and receiver caused a part of the transmitted signal to be reflected back into the receiver. This unwanted signal effectively created a noise threshold which decreased the sensitivity of the receiver. Current methods used in tuning a transceiver are subject to error, are labor intensive and are subject to shift as a result of a particular environment. The subject invention provides the unique combination of structure and advantages of eliminating signal feedback, thereby improving the sensitivity of the receiver.